Your problem may also be a pre-ignition rattle. Most P.I. rattles are related to an EGR system fault. In theory an EGR fault should set the CEL off; in practice it may not.
With the vehicle sitting stationary and in neutral try revving the engine slowly with the window down. If you have a heat shield rattle this bad then you should be able to hear a rattle or buzz at some point in the RPM range.
If not, then my gambling money is on a P.I. rattle probably due to an EGR problem.